Problem: Christopher has lunch at a restaurant and the cost of his meal is $\$28.00$. He would like to leave a $10\%$ tip. What is his total bill including tip?
The tip amount is equal to $10\% \times \$28.00$ To calculate a $10\%$ tip, move the decimal point in $\$28.00$ one place to the left. $10\%$ $\times \$28.00$ $\$2.80$ The cost of the meal plus the amount of the tip will equal the total bill amount. $\$28.00 + \$2.80 = $ $\$30.80$ The total cost of the bill is $\$30.80$.